Method of making ornamental hollow plastic articles

ABSTRACT

A process for making a hollow, ornamental, plastic article which has a smooth interior surface to which is bonded a randomly arranged layer of pellets forming the outer surface and extending outwardly therefrom. The pellets provide a radiating and lighting surface to dissipate heat from a light source positioned within the article and diffusing the light. The article is produced by placing a layer of plastic powder upon a heated surface of a mold in the form of the article, heating the layer to make it tacky and distributing a layer of pellets of a compatible plastic material over the tacky layer of powder, and heating the pellets until they become soft and cooling the mold and article so that the pellets adhere to each other and to the layer and removing the article from the mold.

' llnited States Patent 91 Walters 11] 3,791,399 [451 team, R974 METHODOF MAKHNG ORNAMENTAL HOLLOW PLASTIC ARTICLES [76] Inventor: Ben Walters,4600 E. 1 1th Ave Miami Beach, Fla. 33013 [22] Filed: Apr. 15, 1971 [21]Appl. No.: 134,187

[52] US. Cl 156/152, 156/242, 156/264,

156/304, 156/250, 264/113, 264/126, 264/152 [51] Int. Cl. B29c 21/00[58] Field of Search... 264/1 12, 113, 126, 118, 308, 1 264/241, 152

[56] References Cited UNITED STATES PATENTS 2,761,177 9/1956 Walters264/126 3,414,642 12/1968 Baum 264/126 8/1969 Irving, Jr. et al. 264/126Primary Examiner-Robert F. White Assistant Examiner-J. R. Hall [57]ABSTRACT I A process for making a hollow, ornamental, plastic articlewhich has a. smooth interior surface to which is I bonded a randomlyarranged layer of pellets forming the outer surface and extendingoutwardly therefrom.

The pellets provide a radiating and lighting surface to dissipate-heatfrom a light source positioned within the article and diffusing thelight The article is produced by placing a layer of plastic powder upona heated surface of a mold in the form of the article, heating the layerto make it tacky and distributing a layer of pellets of a compatibleplastic material over the tacky layer of powder, and heating the pelletsuntil they become soft and cooling the mold and article so that thepellets adhere to each other and to the layer and removing the articlefrom the mold.

5 Claims, 8 Drawing Figures msmen m1 2 INVENTOR. BEN WALTERS ATTORNEY.

METHOD OF MAKING ORNAMENTAL HOLLOW PLASTIC ARTICLES outside surface.

In the prior art when it was desired to form a hollow plastic article, arotational molding was used in which a charge of a synthetic materialwas introduced into the cavity of a multi-part sectional hollow mold.The quantity of the charge was less than required to fill the cavity andform the skin of a desired thickness over the periphery of the cavity ofthe mold. The mold was then rotated about a plurality of axes at whichtime the mold with its charge was heated to gel and then fuse. Thereuponthe mold was removed from the heating chamber,- cooled to below thefusing temperature .of the charge and the mold was opened and thefinished article removed. The completed article had a fully fused,essentially homogeneous skin. Also, there has been shown in the priorart a method of making a porous hollow article made from plastic inwhich a granular material was introduced into the'cavity and heatedsufficiently to fuse the particles together but not sufficiently tomelt. However, with this process, while the inner surface remainsroughened, the outer surface was smooth similar to the surface of themold.

The present invention produces a different product from that justdescribed in which the outer surface, i.e. surface facing the viewer, isroughened and the article takes the shape of any form of the mold suchas hollow, pyramidal, trapezoidal or the like. By the term hollowarticle is meant a-self-form maintaining hollow molded articlecharacterized by a shell having a smooth inner surface and having acourse grained outer surface. The outer particles retain their beforemolding individuality andthe particles are randomly arranged. Theserandomly arranged particles permit reflective passages of rays of lightthrough the openings and diffuses any light passing through theparticles, as well as radiating heat to a greater extent than heretoforeand preventing any hot spots on the inner surface even though adjacent alarge wattage bulb for continuous long periods.

Accordingly, it is an object of the present invention to provide aprocess for making an ornamental plastic article having a smoothinterior surface and having granular, randomly located'particles on theouter surface.

A further object of the present invention is to provide a process formaking an ornamental plastic article having a smooth interior surfaceand a roughened outer surface utilizing inexpensive molds whichfaithfully conform to the mold surface.

Another object of the present invention is to provide a process formaking a hollow plastic article of predetermined, reproducible formwhich has a smooth interior surface and a roughened outer surface, whichouter surface provides good radiation of heat from an incandescent lightbulb in the interior of the article, as well as providing unusualilluminating effects by diffusing the light therefrom.

A still further object of the present invention is to provide a processfor producing a relatively inexpensive, highly ornamental plastic coatedarticle having roughened heated surface of various shapes.

Yet another object of the present invention is to provide a process thatproduces a highly ornamental plastic article of reproducible form thataccomplishes all of the above, which utilizes inexpensive and unskilledlabor, and low cost materials, molds and apparatus.

Further objects and features of the present invention will becomeapparent when the following description is considered in connection withthe annexed drawings in which:

FIG. 1 is one type of mold;

FIG. 2 illustrates coating the mold;

FIG. 3 illustrates the following step in which beads or roughenedparticles are distributed on the coating about the mold;

FIG. 4 illustrates removing the plastic article from the mold;

FIG. 5 illustrates the plastic article removed from the mold;

FIG. 6 illustrates an article coated in accordance with the process ofthis invention;

FIG. 7 illustrates another plastic coated article made in accordancewith the present invention; and

FIG. 8 is a fragmentary enlarged portion of a surface made by thedisclosed process.

The present tacky, in essence comprises a process for making anornamental, hollow article by initially dispersing an even layer ofpowdered plastic material over a heated mold of the desired shape andheating the powder until it is tacky dispersing an even layer of plasticpellets over the tacky layer, heating the pellets until the adhere tothemselves and the layer and cooling these pellets and layer to form anintegral sheet and removing the sheet from the mold.

FIGS. 1-5 illustrate one form of the present invention to make a hollowornamental article. FIG. 1 illustrates one mold for making a hollowspherical article in accordance with the present invention. A highlypolished sphere 12 has a threaded opening 14 in which a threaded handle16 is received. Disposed about the outer surface of sphere I2 is agroove 18 contained within a plane generally normal to the axis ofhandle 16. Sphere 12 is heated to a temperature above the melting pointof the plastic tobe used, in any convenient manner, such as in an oven,in high temperature liquid bath, radiation or the like. The outerperiphery of sphere 12 is then coated with a uniform thin layer 20 ofpowdered plastic material. The powder becomes tacky and fuses on theheated mold surface to form a continuous uniform film. The temperatureof the plastic coating material becoming tacky depends on the type ofplastic used, the thickness of the coating to be applied and shape, massand specific heat of the mold. The plastic coating is heated so as toremain tacky. Pellets or particles 22 of suitable plastic material arethen spread evenly over the tacky layer 20. The particles 22 could comein a variety of shapes and forms, such as ovals, discs, stars,triangles, cylinders, turnings, etc., as well as colors, either uniform,mixed or variegated. However, preferably the particles comprising onecharge are of similar form which is believed to provide the mostpleasing appearance. By controlling the heat the particles become tackyand are bonded at their points of contact to form a sheet of semi-fusedparticles and which are also welded and fused to the tacky powderedlayer 20. The particles retain some semblance of their originalappearance as seen best in FIGS. 3 and 5.

The next step is cooling the mold and the exterior of the article tobelow the freezing temperature of the thermoplastic material. This couldbe more efficiently accomplished if the mold were hollow and liquid orair of different temperatures passed therethrough. Also the mold withthe article can be immersed in a large cooling tank not shown. To removethe article, a sharp instrument such as a knife is used to cut alonggroove 18 and form a pair of hemispheres 24 and 26 so that both thelower portion 24 and the upper portion 26 can i be removed from mold 12and then reassembled by adhesive, heat or the like to form a singleunitary article illustrated in FIG. 5. The opening 27 in hemisphere 26allows entrance of a bulb 50, and allows a lamp to be fabricated in aconventional manner. The particles 22 provide varying degrees of lightas well as diffusing the heat from the interior when a large wattageincandescent bulb is used.,

As shown in FIG. the inner peripheral surface of article 28 is smoothand the outer peripheral surface is roughened which is in contrast withthe conventional rotational molding articles heretofore made.

The present process can be used to provide unusual skin effects forvarying shapes such as wastepaper baskets, coasters, decorative articlessuch as lamp bases, lamp shades and the like. The steps would be to'havethe metal wire or bars or strips formed in a predetermined shape, suchas a wire basket or pot holder, illustrated in FIG. 6 in which the wireor metal 30 is heated, then powdered plastic material is disposed on thesurface of the metal in an even thin layer and covering the surface. Thepowder is heated so that it becomes tacky and then pellets 34, ofsuitable plastic material are spread evenly over the tacky layer 32.These pellets when heated become softened and are fused or welded toeach other and to the tacky powdered layer 32. Upon cooling, the tackypowdered layer is permanently and firmly adhered to the metal strips 30,as well as to the pellets 34 making a unitary bond to the metal therebypermitting a variety of intricate designs to be made from inexpensivesoft metals and providing innumerable surface designs and appearance tothe article.

A still further embodiment is illustrated in FIG. 7 showing a glass ormetal surface containing a design, here illustrated to show the lettersBEN. This effect can be obtained by selectively placing plastic stripsof material on the surface to be coated. The glass or metal article 38is heated and a powdered plastic material is disposed on the uppersurface of the glass in an even thin layer 40 covering the surface. Thepowder, of course, does not take on the decorative design 36. The layer40 is heated so as to become tacky and the pellets 42 are placed on thislayer to form a unitary sheet. The entire sheet is covered with theseplastic pellets except for the decorative design 36. While thedecorative design 36 is shown as letters, other designs, such asbutterflies, birds, stars or the like, can be used. If desired, designs36 can be coated with powder, heated until tacky and beads or pellets ofa different color applied, to this surface. Hence, glasses, bottles,vases and the like can have a decorative surface bonded thereto withvarious designs appearing in the surface.

Also, different colored designs can be used where pellets of one coloror shape can be applied to one type of surface and then removing thedecorative or protective coating and then a second color or type ofpellet can be applied to the other surface to provide variations indesign or appearance. While clear or colorless plastic has been used andproduces highly effective results, a mixture of varied-colored plasticgranules will yield a variegated article and further adds additionalcoloring to the article itself.

While plastic materials such as high density polyethylene has been usedeffectively, other thermoplastic materials can be used such as celluloseacetate, cellulose acetate butyrate, polyvinyl, polypropylene,polybutylene, styrene, acrylic, ABS polymers, ethyl cellulosepropionate, chlorinated polyether, polyvinyl chloride, polyvinylidenechloride, copolymers of methyl methacrylate and styrene, copolymers ofbutadiene and polystyrene, polyamide, and polycarbonate. Pigments ordyes in the material will yield any desired color in the finishedproduct, and the use of differently colored coarse grained particleswill engender a multi-colored appearance of the finished article.Further, the particles may be opaque, translucent or transparent, or amixture thereof, all of which will have an influence upon the estheticeffect-of the finished article. Any density of thermoplastic materialmay be utilized depending on the desired stiffness of the finishedproduct.

The present invention eliminates any waste of plastic material since thepowder and pellets are distributed only over the entire surface of themold and any unadhered materials can be collected and reused.

The roughened outer surface allows effective dissipation ,of heat. Forinstance, a hollow sphere made with the present invention was placedover a naked watt incandescent light bulb and dissipated the heat fromthe light bulb so as to prevent-any hot spots on the article andprevented distortion of the article even when a 60 wa t tbu lb burnedcontinuously for48 hgurs. Additionally, the particles diffused the raysof light differen tly than the inner skin, so as to provide a highlyoriginal lighting effect.

Additionally, the use of placing an electrostatic charge on the powderprior to disposing it on the outer surface of the mold, avoids initiallyheating the mold and allows uniform placement of the thin layer ofpowder and then heating the mold. The powder can be applied andpositioned on the mold surface by electrostatic placement or spraying.

While the preferred embodiments have been described above, it isunderstood that many variations thereof will be readily apparent tothose skilled in the art without departing from the spirit thereof.Therefore, it is intended that the foregoing description shall be deemedillustrative only and not construed in a limiting sense, the presentinvention being defined solely by the appended claims.

What I claim is:

1. A process for producing a smooth inner surface, rough outer surface,ornamental, hollow article, comprising:

a. heating the outer surface of a male mold surface having the innerconfiguration of the hollow article;

b. depositing as a first layer, a thin layer of a thermoplasticcomposition in a finely divided state on the heated outer surface ofsaid mold;

c. heating said first layer to cause the layer to fuse and become tacky;

cles of plastic composition over said first tacky layer;

e. heating said second layer particles to become soft without completecoalescence thereof to form a layer of said coarse particle upon saidfirst layer and be bonded thereto;

f. cooling said first and second layers to form coherent surfacecovering said mold surface; and

g. removing said coherent surface covering from said mold surface,whereby a smooth inner surface, rough outer surface hollow article isformed.

2. A process in accordance with claim 1 wherein step (g) entails cuttingsaid coherent surface.

3. A process for producing a smooth inner surface, rough outer surface,ornamental, hollow article comprising:

a. heating the outer surface of a curved male mold surface having theinner configuration of the hollow article; I

b. depositing as a first layer, a thin layer of a thermoplasticcomposition in finely divided state on the heated outer surface of saidmold;

c. heating said first layer to cause the layer to fuse and become tacky;

d. depositing as a second layer, a layer of coarse particles of plasticcomposition over said first tacky layer;

e. heating said second layer particles to become soft without completecoalescence thereof to form a layer of said coarse particles upon saidfirst layer and be bonded thereto;

f. cooling said first and second layers to form a coherent surfacecovering said mold surface;

g. cutting said coherent surface covering into substantially equallydivided portions and removing said portions from said mold surface; and

h. rejoining said portions to form said hollow article.

4. The process in accordance with claim 3 wherein step (e) includescontrolling the heating of the particles to produce bonding at theirpoints of contact, which, when cooled by step (f) forms a sheet ofsemi-fused particles.

5.'A process in accordance with claim 3 further including:

i. initially covering selected portion of the outer surface of said moldsurface with a material to which said first layer is non-adherent.

2. A process in accordance with claim 1 wherein step (g) entails cuttingsaid coherent surface.
 3. A process for producing a smooth innersurface, rough outer surface, ornamental, hollow article comprising: a.heating the outer surface of a curved male mold surface having the innerconfiguration of the hollow article; b. depositing as a first layer, athin layer of a thermoplastic composition in finely divided state on theheated outer surface of said mold; c. heating said first layer to causethe layer to fuse and become tacky; d. depositing as a second layer, alayer of coarse particles of plastic composition over said first tackylayer; e. heating said second layer particles to become Soft withoutcomplete coalescence thereof to form a layer of said coarse particlesupon said first layer and be bonded thereto; f. cooling said first andsecond layers to form a coherent surface covering said mold surface; g.cutting said coherent surface covering into substantially equallydivided portions and removing said portions from said mold surface; andh. rejoining said portions to form said hollow article.
 4. The processin accordance with claim 3 wherein step (e) includes controlling theheating of the particles to produce bonding at their points of contact,which, when cooled by step (f) forms a sheet of semi-fused particles. 5.A process in accordance with claim 3 further including: i. initiallycovering selected portion of the outer surface of said mold surface witha material to which said first layer is non-adherent.